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Allyson Felix talks about life and going gold in Rio

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The US was hit by Brazil during the 4x100-meter relay, causing a botched handoff

The US appealed the result and allowed to re-run race

(CNN)The anguish was clear on Allyson Felix's face -- but the relief will be even more palpable.

Team USA are into the women's 4x100m relay final Friday, but only after a bizarre day on the track in Rio.

It all started Thursday morning.

Felix, the second leg on Team USA's 4x100-meter relay team, was about to hand off the baton to her teammate, English Gardner.

But then, disaster struck. Just as she was about to pass the baton, Felix was hit by a Brazilian runner who veered into the US lane. It caused Felix to trip, bungling the exchange. The baton was dropped.

American Allyson Felix tries to hand the baton to teammate English Gardner in a 4x100-meter relay heat. The U.S. team was disqualified after dropping the baton, but it won an appeal after officials ruled the pair had been obstructed by a Brazilian runner during the exchange. They later clinched a spot in the final after a re-run.

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Photos:Rio Olympics: Day 13

Jonathan Brownlee of Great Britain competes in the triathlon. He took home the silver medal. His brother Alistair won the gold.

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Photos:Rio Olympics: Day 13

Kerron Clement of the United States celebrates winning gold in the 400-meter hurdles.

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Photos:Rio Olympics: Day 13

Puerto Rico's Javier Culson reacts after being disqualified in the 400-meter hurdles final.

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Photos:Rio Olympics: Day 13

Indian badminton player P. V. Sindhu plays a semifinal match against Japan's Nozomi Okuhara. Sindhu won, and she will face Spain's Carolina Marin in the gold-medal match on Friday.

Jamaica comfortably won the first heat of the 4x100 in 41.79. In the second heat, which included the US, Germany won in 42.18. The other teams that have qualified for the final are Great Britain, Ukraine, Nigeria, Trinidad and Tobago, and Canada.